Effect of weather conditions and application of ethrel (Cl-CH₂-CH₂-H₂PO₃) on flowering of lychee in Luc Ngan district, Bac Giang province

In recent years, agricultural production in Vietnam has been greatly influenced by global climate change. In the North, the winter season has seen increase in temperature and frequency of heavy rains, having serious impacts on flowering and fruit set of many fruit trees, including lychee. From 2015 to 2019, continuous changes in winter weather conditions have affected flowering, hence yield and and production of lychee. In 2017 and 2019, proportion of lychee trees that initiated flowers in Luc Ngan districts, Bac Giang province was relatively low, only at 20-60% varying on the orchards and weather conditions in winter, significantly reducing the yield and productivity. In 2016 and 2018, lychee was recorded with high flowering rate, at over 90% plants producing flowers, which was the result of the cold and dry winter season. Solutions to increasing flowering rate on lychee in warm winter conditions have been identified as mechanized and chemical measures. Application of ethrel at different concentrations in warm, rainy winter season inhibited vegetative growth, hence, improving flowering rate on lychee in comparison to the control. Application of ethrel at 600 ppm was recorded with the flowering rate of 62.3%, meanwhile the value obtained in the control was only 36.7%.